{"id":85,"date":"2019-11-15T18:25:43","date_gmt":"2019-11-15T17:25:43","guid":{"rendered":"https:\/\/web.infn.it\/T_CONVERSE\/?page_id=85"},"modified":"2019-11-20T18:34:14","modified_gmt":"2019-11-20T17:34:14","slug":"cryogenic-systems","status":"publish","type":"page","link":"https:\/\/web.infn.it\/T_CONVERSE\/pagina-di-esempio\/cryogenic-systems\/","title":{"rendered":"Cryogenic Systems"},"content":{"rendered":"\n

In dealing with superconducting hybrid systems, an experimental apparatus able to reach cryogenic temperatures is mandatory. In fact, not only the critical temperature of the superconductors has to be reach, but also we need to move towards temperature ranges where the thermal coupling among electrons, phonons and photons thermal components are more suitable for our goals. Usually this means we need to use a cryostat whose temperature can be set from tens of mK to some K.
Cryostat we use are dillution refrigerator with a 3<\/sup>He-4<\/sup>He mixture. <\/p>\n\n\n\n

A\u00a03<\/sup>He-4<\/sup>He dillution refrigerator takes advantage from the unique features of the 3<\/sup>He-4<\/sup>He mixture. In fact, for temperature lower than 870 mK, two thermodynamical phases coesist in the mixture, which differ for the 3<\/sup>He concentration: as the temperature gets lower, the concentrate <\/em>phase becomes more and more rich of 3<\/sup>He whereas the diluite <\/em>phase becomes poorer of it since it reaches the limited 6.6% concentration [1]. By pumping on the mixture, a transfer of 3<\/sup>He from a phase to the other achieves an endothermic cycle which cools down the temperature.
In our measurements we use a cryostat by Leiden Cryogenics<\/a> and by Oxford instruments<\/a>, where the 3<\/sup>He- 4<\/sup>He dillution machanism is the last step of the cooling down process and where a base temperature of 10 mK can be reached. <\/p>\n\n\n\n

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Left:<\/strong> Phase diagram of the 3<\/sup>He-4<\/sup>He mixture. The red circled point, T=0.87 K, marks the beginning of the two-phase region. For temperatures lower than 0.87K the mixture shoes a 3<\/sup>He-rich phase (yellow arrow) and a 3<\/sup>He-poor phase (light blue arrow), which are named concentrate and diluite phase, respectively. As the temperature tends to zero K, the 3<\/sup>He-concentration of the two phases changes: the concentrate phase reaches the 100% value and the diluite one reaches the saturation value 6.6%. Adapted from [1]. Right:<\/strong> Scheme of the
3<\/sup>He-4<\/sup>He dilution cryostat Triton 200, by Oxford Instruments. The cryostat is made by a series of nested metallic shells. Each plate showed in the picture represents a stage in the cooling down process, the coolest plate is the innest one. which connected by pipes and probes Adapted from [2]. <\/figcaption><\/figure>\n\n\n\n

[1] Frank Pobell. Matter and Methods at Low Temperatures<\/em><\/a>, Springer.
[2] Triton 200 product guide, Oxford Instruments, 2012.<\/p>\n","protected":false},"excerpt":{"rendered":"

In dealing with superconducting hybrid systems, an experimental apparatus able to reach cryogenic temperatures is mandatory. In fact, not only the critical temperature of the superconductors has to be reach, but also we need to move towards temperature ranges where the thermal coupling among electrons, phonons and photons thermal components are more suitable for our […]<\/p>\n","protected":false},"author":2,"featured_media":0,"parent":2,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-85","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/web.infn.it\/T_CONVERSE\/wp-json\/wp\/v2\/pages\/85","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/web.infn.it\/T_CONVERSE\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/web.infn.it\/T_CONVERSE\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/web.infn.it\/T_CONVERSE\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/web.infn.it\/T_CONVERSE\/wp-json\/wp\/v2\/comments?post=85"}],"version-history":[{"count":14,"href":"https:\/\/web.infn.it\/T_CONVERSE\/wp-json\/wp\/v2\/pages\/85\/revisions"}],"predecessor-version":[{"id":170,"href":"https:\/\/web.infn.it\/T_CONVERSE\/wp-json\/wp\/v2\/pages\/85\/revisions\/170"}],"up":[{"embeddable":true,"href":"https:\/\/web.infn.it\/T_CONVERSE\/wp-json\/wp\/v2\/pages\/2"}],"wp:attachment":[{"href":"https:\/\/web.infn.it\/T_CONVERSE\/wp-json\/wp\/v2\/media?parent=85"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}